Forest conversion may affect the soil microbial community through impacts on soil properties. However, our understanding of the effects on the soil bacterial community remains limited. The objective ...of this study was to understand the impacts of forest conversion of native broad-leaved species on soil bacterial structure and diversity. The phylogeny structure and diversity of the soil bacterial communities were compared among four forest types. We found that the soil total nitrogen (TN) and C:N ratios were significantly different between a mixed forest and other forest types. The native forest and mixed forest contained a higher relative abundance of Actinobacteria, Gammaproteobacteria, and Acidimicrobiia compared with the Chinese fir and Bamboo forests, but more unique operational taxonomic units (OTUs) were found in the Chinese fir and Bamboo forests. Soil bacteria in bamboo forest and Chinese fir forest showing a higher diversity but a lower total sequencing number than native forest and mixed forest. Among the soil properties, pH was an important variable that contributing to both soil bacterial communities and soil alpha diversities. Our work suggests that after a long-tern forest conversion, both land-use history and vegetation species strongly influence soil bacteria communities, and soil pH is a main factor that influences soil bacterial structure.
•Forest conversion has a profound impact on soil bacterial composition.•Land use history has a long lasting influence on soil bacteria OTUs.•Change to a pure forest did not cause a decrease in soil bacterial diversity.
•Phospholipid fatty acid profiling analysis was applied to determine the composition of microbial communities.•The relative abundance of anaerobic bacteria and 16:1 ω5c in native broad-leaved forest ...was distinct from converted forests.•Land use change can have a profound impact on soil microbial composition.
Soil microbial communities play vital roles in nutrient cycling and ecosystem functioning but these communities could be affected by land use change. To understand the impacts of land use change on soil microbial communities, we assessed the relative abundance of soil microbial communities and soil physicochemical properties following stand conversion from native broadleaf forests to mixed and bamboo forests in Feng yang Mountain Nature Reserve, China. We used phospholipid fatty acid (PLFA) profiling analysis to determine the composition of microbial communities, quantified soil bulk density, pH, organic carbon, nitrogen, and phosphorus concentrations to determine soil physicochemical properties, and assessed species richness and evenness to determine vegetation structure. We found that the abundance of anaerobic bacteria was significantly higher in the bamboo forests than in broad-leaved or mixed forests, while the abundance of 16:1 ω5c was significantly lower in the mixed forests than other forests. The relative abundance of 16:1 ω5c was positively correlated with soil pH, while the abundance of anaerobic bacteria was negatively correlated with soil phosphorus concentration. Among the three different land use types, bamboo forest was characterized by significantly higher soil pH, while the broad-leaved forest had significantly higher nitrogen concentration, and mixed forest had significantly higher soil bulk density. Overall, the composition of microbial communities in native broad-leaved forest was distinct from converted forests in the relative abundance of anaerobic bacteria and 16:1 ω5c, underscoring the fact that land use change can have a profound impact on soil microbial composition.
Saturated hydraulic conductivity (K
) is one of the most important soil properties that determines water flow behavior in terrestrial ecosystems. However, the K
of forest soils is difficult to ...predict due to multiple interactions, such as anthropological and geomorphic processes. In this study, we examined the impacts of vegetation type on K
and associated mechanisms. We found that K
differed with vegetation type and soil depth, and the impact of vegetation type on K
was dependent on soil depth. K
did not differ among vegetation types at soil depths of 0-10 and 20-30 cm, but was significantly lower in managed forest types (mixed evergreen broad-leaved and coniferous forests, bamboo forests, and tea gardens) than native evergreen broadleaf forests at a depth of 10-20 cm. Boosted regression tree analysis indicated that total porosity, non-capillary porosity, and macro water-stable aggregates were the primary factors that influenced K
. Our results suggested that vegetation type was a key factor that influences hydraulic properties in subtropical forest soils through the alteration of soil properties, such as porosity and macro water-stable aggregates.
Dendrobium moniliforme (Linnaeus) Swartz is a well-known plant used in traditional Chinese medicine due to bioactive constituents. Polysaccharides are the main medicinal ingredients, yet no studies ...have been published on polysaccharide biosynthesis in D. moniliforme. To comprehensively investigate the polysaccharide at the transcription level, we performed de novo transcriptome sequencing for the first time to produce a comprehensive transcriptome of D. moniliforme.
In our study, a database of 562,580 unigenes (average length = 1115.67 bases) was generated by performing transcriptome sequencing. Based on the gene annotation of the transcriptome, we identified 1204 carbohydrate-active related unigenes against CAZy database, including 417 glycosyltransferase genes (GTs), 780 glycoside hydrolases (GHs), 19 carbohydrate esterases (CEs), 75 carbohydrate-binding modules (CBMs), and 44 polysaccharide lyases (PLs). In the cellulose synthase family, 21 differential expression genes (DEGs) related to polysaccharide were identified. Subsequently, the tissue-specific expression patterns of the genes involved in polysaccharide pathway were investigated, which provide understanding of the biosynthesis and regulation of DMP at the molecular level. The two key enzyme genes (Susy and SPS) involved in the polysaccharide pathway were identified, and their expression patterns in different tissues were further analyzed using quantitative real-time PCR.
We determined the content of polysaccharides from Dendrobium moniliforme under different tissues, and we obtained a large number of differential genes by transcriptome sequencing. This database provides a pool of candidate genes involved in biosynthesis of polysaccharides in D. moniliforme. Furthermore, the comprehensive analysis and characterization of the significant pathways are expected to give a better insight regarding the diversity of chemical composition, synthetic characteristics, and the regulatory mechanism which operate in this medical herb.
The methylerythritol phosphate (MEP) pathway provides the universal basic blocks for the biosynthesis of terpenoids and plays a critical role in the growth and development of higher plants.
is the ...most valuable oleoresin producer tree with an extensive terrestrial range. It has the potential to produce more oleoresin with commercial value, while being resistant to pine wood nematode (PWN) disease. For this study, eleven MEP pathway associated enzyme-encoding genes and ten promoters were isolated from
. Three
and two
existed as multi-copy genes, whereas the other six genes existed as single copies. All eleven of these MEP enzymes exhibited chloroplast localization with transient expression. Most of the MEP genes showed higher expression in the needles, while
,
, and
had high expression in the roots. The expressions of a few MEP genes could be induced under exogenous elicitor conditions. The functional complementation in a
-mutant
strain showed the DXS enzymatic activities of the three
. High throughput TAIL PCR was employed to obtain the upstream sequences of the genes encoding for enzymes in the MEP pathway, whereby abundant light responsive
-elements and transcription factor (TF) binding sites were identified within the ten promoters. This study provides a theoretical basis for research on the functionality and transcriptional regulation of MEP enzymes, as well as a potential strategy for high-resin generation and improved genetic resistance in
.
Background
Soil acidification caused by acid rain (AR) can damage plant roots, which in turn negatively impacts plant health. In response to changing AR types, research efforts to elucidate their ...specific impacts on plants have become intense.
Methods
For this study, we investigated the effects of simulated sulfuric, nitric, and mixed AR on the root systems of
Quercus acutissima
Carr. and
Cunninghamia lanceolata
(Lamb.) Hook. under different acidity levels.
Results
As the AR S/N ratio and pH decreased, the height growth rate (HGR), basal diameter growth rate (DGR), total root length (TRL
)
and total root surface area (TRS) of
C. lanceolata
decreased, whereas the TRL and TRS of
Q. acutissima
remained the same. When the NO
3
−
concentration in AR was increased, the root activity, superoxide dismutase (SOD) and catalase (CAT) activities of
C. lanceolata
roots revealed a downward trend; however, the root activity of
Q. acutissima
and the peroxidase (POD) activity of
C. lanceolata
roots revealed an upward trend. Further, redundant analysis and structural equation models indicated that AR pH had a greater impact on the HGR of
Q. acutissima
than that of
C. lanceolata
, while the impact of the AR S/N ratio on
C. lanceolata
growth rates was greater than that of
Q. acutissima
.
Conclusions
Our results suggested that the root systems of different tree species had variable responses to AR, and the AR S/N ratio was an important factor affecting plant root growth. This might facilitate new strategies for the cultivation and protection of plantations in the future.
Soil aggregates are the basic structural components of soil, which are important factors that can predict erosion resistance. However, few researchers have investigated the effects of forest ...conversion on the stability of soil aggregates, particularly in subtropical forests. In this study, soils from various depths (0 to 30 cm) were collected from four forest types (transformed from broadleaved forests (BMF) to combined coniferous broadleaved (CBMF), Chinese fir (FF), and bamboo forests (BF)) to determine the impacts of forest conversion on the physical and chemical properties of soil, water-stable soil aggregates, and aggregate-associated humic substances. The results showed that forest conversion had no effects on the soil’s physical properties, or the humic substances in bulk soil, but had significant effects on soil aggregates. In addition, the conversion of broadleaved forest to Chinese fir forest increased the soil stability, and to bamboo forest, decreased the soil stability. Finally, the soil’s physicochemical properties were closely related to aggregate-associated humic substances. In summary, specific forest management measures should be applied to strengthen the positive impacts and reduce the negative impacts associated with forest conversion.
The stability of soil aggregates is critical for maintaining soil structures and is positively correlated with soil resident organic and inorganic colloids. Forest conversion and soil depth affects ...the formation of soil aggregates; however, the detailed mechanisms involved in their stabilization have not been well investigated. Therefore, to explore the main factors that influence the stability of soil aggregates for different forest types and soil depths, twelve soil samples were collected from four types of forests (native, mixed, Chinese fir, and bamboo forest) and three soil depths (0–10 cm, 10–20 cm, and 20–30 cm) in subtropical forests. The results revealed that the distributions and mean weight diameters (MWDs) of large macroaggregates in the bamboo forest were significantly lower than those in the other forest types at all soil depths (p < 0.05). Organic and inorganic colloids (organically-complexed Fe oxide and fulvic acid) in the soil directly impacted the stability of soil aggregates, while soil properties (e.g., pH and bulk density) indirectly promoted soil aggregate stability through the modification of colloids. In both native and bamboo forests, organic colloids contributed most to the stability of soil aggregates, reaching 80.31% and 61.37%, respectively. The contributions of organic colloids were found to decrease with soil depth, which was primarily due to changes in the organic matter caused by the decomposition of litter. Elucidating and promoting the specific contributions of organic and inorganic colloids on the stability of soil aggregates will be increasingly important for the optimal management of different forest types.
Acid rain and nitrogen deposition are emerging as global scale environmental issues due to increasing industrial emissions and agricultural pollutants, which seriously impac t the sustainable ...development of global ecosystems. However, the specific effects both acid rain and nitrogen deposition interactions on forest soil ecosystems, particularly as relates to the soil nutrient content and enzyme activities, remain unclear. Therefore, we established a simulated sample plot of acid rain (SR, NR) and nitrogen deposition (N) and their interactions (SRN, NRN) in a subtropical Cunninghamia lanceolata ( C. lanceolata ) plantation in the Yangtze River Delta region of China to investigate the impacts of these factors via correlation analysis and structural equation model (SEM). The results showed that acid rain had a stronger effect on soil pH than nitrogen deposition in C. lanceolata plantation, while the simultaneous addition of acid rain and nitrogen deposition exacerbated soil acidification. Soil available potassium, ammonium nitrogen and nitrate nitrogen in C. lanceolata plantation responded more obviously to acid rain and nitrogen deposition, in which acid rain, nitrogen deposition and their interactions significantly reduced soil available potassium content, while acid rain and nitrogen deposition interactions significantly increased soil ammonium nitrogen and nitrate nitrogen content. Nitric acid rain, nitrogen deposition and their interactions significantly increased soil NAGase activity, but significantly decreased soil urease activity; the single-factor treatment of acid rain and nitrogen deposition significantly increased soil arylsulfatase activity, while the interaction of acid rain and nitrogen deposition significantly decreased soil arylsulfatase activity; in general, the interaction of acid rain and nitrogen deposition had a stronger effect on the soil ecosystem of the C. lanceolata plantation than that of single acid rain or nitrogen deposition, of which nitrogen deposition exacerbated the effects of acid rain on the soil ecosystem of C. lanceolata plantation mainly by changing the soil pH and the content of effective nutrients.
Background
China has been increasingly subject to significant acid rain, which has negative impacts on forest ecosystems. Recently, the concentrations of NO
3
−
in acid rain have increased in ...conjunction with the rapid rise of nitrogen deposition, which makes it difficult to precisely quantify the impacts of acid rain on forest ecosystems.
Methods
For this study, mesocosm experiments employed a random block design, comprised of ten treatments involving 120 discrete plots (0.6 m × 2.0 m). The decomposition of fine roots and dynamics of nutrient loss were evaluated under the stress of three acid rain analogues (e.g., sulfuric (SO
4
2−
/NO
3
−
5:1), nitric (1:5), and mixed (1:1)). Furthermore, the influences of soil properties (e.g., soil pH, soil total carbon, nitrogen, C/N ratio, available phosphorus, available potassium, and enzyme activity) on the decomposition of fine roots were analyzed.
Results
The soil pH and decomposition rate of fine root litter decreased when exposed to simulated acid rain with lower pH levels and higher NO
3
−
concentrations. The activities of soil enzymes were significantly reduced when subjected to acid rain with higher acidity. The activities of soil urease were more sensitive to the effects of the SO
4
2−
/NO
3
−
(S/N) ratio of acid rain than other soil enzyme activities over four decomposition time periods. Furthermore, the acid rain pH significantly influenced the total carbon (TC) of fine roots during decomposition. However, the S/N ratio of acid rain had significant impacts on the total nitrogen (TN). In addition, the pH and S/N ratio of the acid rain had greater impacts on the metal elements (K, Ca, and Al) of fine roots than did TC, TN, and total phosphorus. Structural equation modeling results revealed that the acid rain pH had a stronger indirect impact (0.757) on the decomposition rate of fine roots (via altered soil pH and enzyme activities) than direct effects. However, the indirect effects of the acid rain S/N ratio (0.265) on the fine root decomposition rate through changes in soil urease activities and the content of litter elements were lower than the pH of acid rain.
Conclusions
Our results suggested that the acid rain S/N ratio exacerbates the inhibitory effects of acid rain pH on the decomposition of fine root litter.
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